The present invention relates to devices deployable in a vessel of the body such as a distal protection device deployable in a blood vessel. In one of its more particular aspects, the invention relates to the positioning of a guidewire or filter within human vasculature.
Any intervention into human vasculature can give rise to the need for capturing and retrieving debris, such as grumous matter, emboli, or thrombi, from the affected vessel. Filters of various types have found use, for example, in trapping blood clots and other debris released into the bloodstream. Many filters, however, can be only partially effective in capturing the debris from surgical or catheterization interventions because deployment of the filter within the blood vessel may not provide complete filtration. That is, a filter may not effect filtration across the full cross-section of the blood flow through the vessel. This may result from failing to maintain an optimum fit of the filter within the vessel wall. Where a filter basket is used, another cause for concern is that the basket may not always be fully opened upon deployment within the vessel.
Specifically, filters are traps that have been designed to be used to collect dislodged matter, such as grumous matter, emboli or thrombi, during procedures such as stent installation in coronary saphenous vein grafts. Such filters or traps serve to provide protection from distal embolization that might result in a major adverse coronary event or other acute complication. Embolization of debris which might be released during such procedures and the resulting sequellae have been described in reports documenting major adverse cardiac event rates. Such events include acute myocardial infarction, revascularization and even death.
In order to address such acute embolic-related complications, distal filtration and protection devices have been developed. Such devices have been designed to work with existing interventional modalities. Such devices provide debris-filtering protection during invasive procedures and are intended to prevent complications of particulate embolization.
Such distal filtration and protection devices are typically deployed at a location along a vessel of the body at a desired location. Such deployment is performed by extending the device outwardly from the distal end of a catheter. In order to facilitate deployment, the device to be deployed typically has components made from a shape-memory or highly elastic material. Consequently, they are able to be collapsed within the catheter and, upon being urged outwardly beyond the distal end of the catheter, they reassume their uncollapsed shape.
Nevertheless, performance of such filtration and protection devices is less than perfect. One significant drawback is the general lack of rigidity of the device. While shape-memory materials are used and the device, once released from the catheter, tends to assume an intended uncollapsed configuration, the path of the vessel within which it is intended to be installed can be tortuous. The guidewire upon which the device is installed, therefore, tends to alternately engage opposite sides of the internal vessel wall as the vessel sinuates back and forth. This circumstance can cause the filtration/protection device to become at least partially collapsed between the guidewire and the internal vessel wall. This can result in at least a portion of the mouth of the device being closed and not fully covering the cross-section of the vessel. At least a portion of flow through the vessel can, then, bypass the device.
At least one other circumstance might result in the filtration/protection device becoming at least partially collapsed and a commensurate closure of at least a portion of the mouth of the device. When the guidewire carries a percutaneous transluminal coronary angioplasty (PTCA) balloon, stent or IVUS catheter, the radial position of the guidewire within the internal vessel can be altered from a desired generally central location. When the guidewire is displaced in this manner, the device can become partially collapsed, as discussed above, with commensurate partial or complete closure of the mouth of the device. Again, at least a portion of flow through the vessel can, thereby, bypass the device.
It is to these problems and dictates of the prior art that the present invention is directed. It is an improved distal protection device deployable in a blood vessel which facilitates maximization of desired filtration/protection.
It is an object of the present invention to provide a distal protection device which can be deployed to fit optimally within a blood vessel or other human vasculature.
Another object of this invention is to provide a distal protection device having a filter basket which is maintained in the fully opened configuration after deployment and during use.
Other objects and advantages of the present invention will become apparent from the following detailed disclosure and description.
The distal protection device of the present invention is provided with a self-expanding member, shown, in one embodiment, as a loop, that creates a radial force against a vessel wall to control the lateral position of a filter at a desired location in a blood vessel. The self-expanding loop functions to maintain open a proximal opening on a distal protection device such as a filter basket. The loop creates a radial force on the device""s guidewire at or near the proximal end of the distal protection device, pushing the guidewire and filter carried by the guidewire against the vessel wall. Any debris formed as a result of proximal intervention, such as by PTCA or stenting, is thereby caused to enter the proximal opening of the basket. Prior to the present invention, the guidewire could be so positioned as to keep the proximal end of the filter basket from opening fully in various tortuous anatomy, resulting in failure to capture debris intended to be captured by the basket.
In one embodiment, the invention includes an element which serves to maintain the filter basket, when deployed, laterally on a defined side of the guidewire. Also included in this embodiment is a collapsible, quasi-rigid loop, or other type of spacer, carried proximate a mouth of the filter basket. The loop or other spacer member is positioned along the guidewire at or proximate the mouth of the filter basket so as to extend laterally on the same side of the guidewire as does the filter basket. Axial alignment of the loop or spacer and filter basket is achieved, in this embodiment, by rigidly fixing the spacer to the element which serves to maintain the filter basket on the defined side of the guidewire, or rigidly fixing the spacer to the guidewire by a separate securing element axially spaced from the filter basket affixation element, but with the spacer axially aligned with the filter basket. It will be understood that the specific loop or other spacer used is provided with a dimension on the side of the guidewire on which it deploys sufficient so as to engage an inner surface of the vessel at a particular circumferential location and, concurrently, urge the guidewire against the inner surface of the vessel at a location generally diametrically opposite that of the location engaged by the spacer.
The self-expanding loop can, as discussed above, be positioned on the guidewire at a location at or proximate the opening of the filter basket or embedded in the braid of the filter basket at or near its proximal end. It will be understood, in view of this disclosure, that the self-expanding loop or other spacer can be made, in one embodiment, to extend on the same lateral side of the guidewire as does the filter basket even when they both rotate concurrently. This can be accomplished by having the spacer attached to an element by which the filter basket is fixed to the guidewire, having the spacer interwoven into the mouth of the filter basket, or having the spacer tethered to the mouth of the filter basket so that, as the filter basket moves rotationally within the vessel of the body, the spacer will commensurately be moved so that substantial axial alignment is maintained.
The loop, while relatively rigid when expanded, is collapsible along with the filter basket for insertion into a delivery catheter. Insertion can be readily accomplished by either front-loading or back-loading. The loop expands upon deployment at a desired treatment location during a medical procedure such as a coronary intervention.
The loop can be constructed in a generally circular shape or can be formed in various xe2x80x9cCxe2x80x9d, xe2x80x9cJxe2x80x9d or spiral configurations, as desired. A continuous loop is preferred.
The loop may extend generally perpendicular to the guidewire when expanded, since, in that position, it exerts the greatest radial force, being deployed perpendicular to the vessel wall, and provides an optimal fit within the vessel. However, although perpendicular deployment is preferred, an adequate radial force can be generated by expansion of the loop at any angle between 45 degrees and 90 degrees relative to the axis of the guidewire.
The loop can be constructed of a single small diameter wire, such as a nitinol wire, or cable, coil, or stranded cable. It can be radiopaque or covered by a radiopaque material, if desired, to enable the viewing of the proximal opening of the distal protection device when deployed during a procedure.
The present invention is thus an improved apparatus for effecting optimum functioning of a distal protection filter basket. The spacer of the present invention makes it likely that the proximal opening of the distal protection device remains fully open while deployed. It expands and positions itself upon deployment. It does not interfere with the operation of the distal protection device, does not interfere with debris capture, and does not interfere with blood flow.